Application of a wet oxidation method for the quantification of 3H and 14C in low-level radwastes

Wet oxidation methods are utilized to separate and quantify 3H and 14C radionuclides in inorganic and organic radwastes generated at nuclear facilities. Because 3H and 14C are pure beta emitters with half-lives of 12.3 and 5,730 years, respectively, these radionuclides should be chemically separated from other radionuclides present in radwastes for accurate quantification. In particular, a collection technique for 14C radionuclide in radwastes is needed because it is converted into 14CO2 gas by an oxidation reaction. To confirm the recoveries of 3H and 14C, various standard radioactive sources were used to verify the proposed method. Because the majority of 3H radionuclides are distributed in tritiated water (HTO), only tritiated water was used as a standard for 3H radionuclides. Additionally, 14C-labeled methanol (14CH3OH), lauric acid (14CH3(CH2)10COOH), sodium bicarbonate (NaH14CO3), and toluene (C6H514CH3) were used as 14C standards. The compounds were oxidized with chemical oxidants and then separated. The individual species were mixed with a scintillation cocktail and counted using a liquid scintillation counter. The recoveries of 14C and 3H were 82–97% and 98%, respectively. The wet oxidation method will be applied to RI wastes for clearance. - Highlights: • The wet oxidation method was developed and verified with various radioactive standards. • The sources were HTO, 14CH3OH, 14CH3(CH2)10COOH, NaH14CO3, and C6H514CH3. • The chemical yield of 14C and 3H were 82–97 % and 98%, respectively. • The wet oxidation method will be applied to RI solid waste for clearance